1. Field of the Invention
This invention relates to a method for the hydroprocessing of organic compounds. This includes all types of petroleum hydrocracking and hydrotreating processes. This process can be used for the low pressure hydrogenation of organic compounds and petroleum using conventional heat sources. This method's performance can be further enhanced using radio frequency (RF) or microwave energy.
2. Description of Related Art
Hydrocarbons are subjected to a variety of physical and chemical processes to produce higher value products. These processes include fractionation, isomerization, bond dissociation and reformation, purification, and increasing hydrogen content. The processes tend to require high pressures and temperatures. Catalysts are employed in the processes for various reasons including, but not limited to, reducing the temperatures and pressures at which the hydrocarbon conversion reaction takes place. The term “hydroprocessing” is used to refer to the encompassing superset of these processes in which hydrogen is used.
Petroleum or crude oil is a naturally occurring mixture of hydrocarbons and smaller amounts of organic compounds containing heteroatoms such as sulfur, oxygen, nitrogen, and metals (mostly nickel and vanadium). The petroleum products obtained from crude oil processing vary considerably, depending on market demand, crude oil quality, and refinery objectives. In current industrial practices, crude oils are submitted to distillation under atmospheric pressure and under vacuum. The distillation fractions (including the residual fractions) undergo further catalytic refining processes so high-value products can be produced.
The hydrogen content of petroleum products is an important index of their economic value. In conventional hydrocracking and hydrotreating processes, the hydrogenation reactions of aromatic compounds play a crucial role. Heavy residual compounds are normally aromatic in nature. The complete or partial saturation of these compounds by hydrogen addition is an important step in their cracking into smaller, more valuable compounds. Conventional heavy oil hydrocracking processes require relatively high temperature (e.g. greater than 400° C.) and very high pressure (e.g. greater than 1000 psi). In current hydrotreating and hydroreforming processes, supported Ni—Mo and Co—Mo sulfided catalysts become active only at the high temperature range. In order for reactions to take place at a favorable lower temperature range, expensive noble metal catalysts are usually used in order to achieve good hydrogenation efficiency. Attempts have been made to find new classes of catalysts that would significantly lower the process parameters, while increasing the hydrogenation efficiency in terms of deep reduction of aromatic content, but the progress made thus far is mostly small improvements over existing catalyst systems.
As the name implies, hydrocracking combines catalytic cracking and hydrogenation by means of a bifunctional catalyst to accomplish a number of favorable transformations of particular value for the selected feedstocks. In a typical bifunctional catalyst, the cracking function is provided by an acidic support, whereas the hydrogenation function is provided by noble metals, or non-noble metal sulfides from Periodic Table Groups 6, 9, and 10 (based on the 1990 IUPAC system in which the columns are assigned the numbers 1 to 18). Hydrocracking is a versatile process for converting a variety of feedstocks, ranging from naphthas through heavy gas oils, into useful products. Its most unique characteristic involves the hydrogenation and breakup of polynuclear aromatics. Significant portions of these feedstocks are converted through hydrocracking into smaller-sized and more useful product constituents. However, some of the large aromatic complexes within these feedstocks, once partially hydrogenated via hydrocracking, can proceed to dehydrogenate forming coke on the catalysts. Coke formation is one of many deactivation mechanisms that reduce catalyst life.
In many refineries, the hydrocracker serves as the major supplier of jet and diesel fuel components (middle distillates). Because of the high pressure required and hydrogen consumption, conventional hydrocrackers are very costly to build and to operate. By developing a class of catalysts with high selectivity for middle distillates and favorable operating conditions, it is possible to significantly reduce these high costs while maximizing the production of the middle distillates.
To remove undesirable heteroatoms, desulfurization, denitrogenation, and demetallization processes are also accomplished using hydroprocessing methods. Because the values of petroleum products are directly related to their hydrogen contents, the effective hydrogenation of products is highly desirable in all stages of petroleum refining.
Metals, such as platinum, deposited on oxide supports, such as alumina or silica, are widely used in catalysts for hydrocarbon reforming reactions. The deposited metal provides reactive sites at which the desired reactions can occur. However, catalysts using these metals have the problem of being rendered inactive if heavy polyaromatic organic compounds build up and occupy or block the sites. The removal of sulfur and sulfur compounds are also a problem for these catalysts. Sulfur reacts with the catalytic sites of Pt or Pd metals and can also deactivate these sites by chemically binding to the metals. Successful catalysis requires that a suitable high local concentration of hydrogen be maintained during the catalytic process. Pressure and temperature conditions are selected to favor formation of the desired product, to provide a suitable rate of conversion, and to avoid rapid deactivation of the catalytic surface.
Hydroprocessing catalysts and their respective components can take many forms and structures. Much is known about optimizing catalyst performance for specific processes (e.g., hydrogenation, hydrocracking, hydrodemetallization and hydrodesulfurization). Regarding the catalyst form, the catalyst can be used as a powder, extrudate, or preformed matrix based upon the type of chemical reactor design selected (e.g., fluidized bed, fixed bed, catalytic converter).
An overall need remains, however, for improved catalysts and catalytic hydroprocesses that can be carried out under relatively mild conditions.